With the ever increasing electrical power load, power generation capacity needs to be scaled up accordingly to always achieve a balance between generation and consumption. No matter for existing or new power plants, it is always desirable to make fully utilization of the generation facilities.
Installing variable frequency drives for large-scale auxiliary motors of the power plant is the most commonly adopted way in industry to achieve this target which can help to reduce the in-house load considerably. Another solution is to reduce the reactive power consumption of the auxiliary system, which also allows the generator to produce more active power while still maintaining the same level of reactive power support to the grid. However, the auxiliary system only counts for a small part of the generation capacity, e.g. around 10% for coal-fired power plants, which limits the potential contribution from the above mentioned solutions in terms of power plant active power output capability improvement.
The present invention proposes a novel solution to achieve this target from generator point of view, i.e. to install SVC at the generation side to share the required reactive power output of the power plant. The main circuit topologies have been disclosed in prior art, such as a PCT application: PCT/US2011/181044, entitled “Method and Apparatus for Improving Power Generation in a Thermal Power Plant”, which was filed on Jan. 21, 2011. Thereafter, the foregoing patent application is incorporated herein by reference.
By operating the generator and the SVC to control the power factor of the generator to improve the active power capability of the power plant, at least three problems need to be solved:
The control references obtained by the coordination controller depend on multiple factors, like the main circuit topologies, the primary controls adopted by the generator and the SVC, etc. While at present no prior art mentions how to ensure the generalization of the designed coordination controller by taking different possible factors into consideration.
The required reactive power output of the SVC varies along with the operation status of the generator and the power system which are connected to the SVC. No prior mentions how to determine the operation point of the SVC to make the generator run at unity power factor in the full operation range.
The third problem to be solved is how to ensure the performance of the coordination controller, which mainly refers to the following two aspects: to guarantee the accuracy based on the accessible information, and to achieve fast response speed without affecting the stable operation of the generator.
Due to the above mentioned problems, a control method for coordinating generator and SVC and a controller thereof are proposed to improve power plant active power throughput in the present invention.